The present invention relates to a polycarbonate having excellent heat resistant stability, a method for preparing and molded products thereof. More specifically, it relates to a polycarbonate which has a specific signal having specific integrated intensity in its 1H-NMR spectrum, rarely experiences a reduction in mechanical strength caused by thermal decomposition and is suitable for the melt molding of a thin product, a method for preparing and molded products thereof.
Polycarbonates are engineering plastics which are excellent in mechanical strength, color and transparency. They have recently been used for various purposes and formed into various molded products. Due to excellent mechanical strength, they are frequently used as a material for thin products such as disk substrates and housings for electric products.
The molding of polycarbonates is mainly melt molding. Since polycarbonates have high melt viscosity, they have low melt fluidity and moldability. Therefore, a thin product is generally formed by melt molding at a high temperature of 250 to 400xc2x0 C. However, it is a heretofore problem that the thermal decomposition of polycarbonates readily occurs at such a high temperature, thereby causing quality deterioration such as a reduction in the mechanical strength of a molded product. Accordingly, the development of a polycarbonate which is stable against thermal decomposition at a temperature range for melt molding has been desired not to reduce the mechanical strength of a melt molded product.
As means of improving the heat resistant stability of a polycarbonate, there has been known a method in which a heat resistant stabilizer is mixed into a polymer. However, a polycarbonate containing a heat resistant stabilizer has such a problem that the heat resistant stabilizer exerts a bad influence upon the characteristic properties such as color, transparency and mechanical strength of the polycarbonate as well as a defect in production process and an increase in cost.
It is disclosed by JP-A 61-87724 and JP-A 61-87725 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) that a terminal hydroxyl group exerts a bad influence upon the heat resistant stability of a polycarbonate. In the melt polymerization method or solid-phase polymerization method in which many terminal hydroxyl groups are essentially existent in the molecule owing to the characteristics of a polymer production process, various methods for reducing the number of terminal OH groups of a polycarbonate have been proposed ardently. It is known that there is limitation to the reduction of the number of OH terminal groups.
Under the situation, the development of a polycarbonate which is stable against thermal decomposition without adding a heat resistant stabilizer to produce a polycarbonate simply at a low cost and taking a special measure of reducing the number of OH terminal groups, suitable for the melt molding of a thin product and produced more easily at a lower cost than existing polycarbonates has been strongly desired.
It is an object of the present invention to provide a polycarbonate which is stable against thermal decomposition at a temperature range for melt molding without adding a heat resistant stabilizer and suitable for the melt molding of a thin product.
It is another object of the present invention to provide an industrially advantageous method of producing the above polycarbonate of the present invention.
It is still another object of the present invention to provide a molded product of the above polycarbonate of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
Firstly, according to the present invention, the above objects and advantages of the present invention are attained by an aromatic polycarbonate which is comprising mainly a recurring unit represented by the following formula (1): 
and has a percentage of the total of integrated intensities of all signals detected at four ranges, xcex4=2.14 to 2.17 ppm, xcex4=3.46 to 3.49 ppm, xcex4=3.62 to 3.69 ppm and xcex4=5.42 to 5.46 ppm to the integrated intensity of a signal derived from a methyl group detected at a range of xcex4=1.50 to 2.00 ppm of 0.01 to 2.0% in its 1H-NMR spectrum in heavy chloroform and a viscosity average molecular weight of 10,000 to 100,000.
Secondly, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as xe2x80x9cfirst production method of the present inventionxe2x80x9d hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and, as a co-catalyst, a sulfur-containing compound, the alkali metal compound being used in an amount of 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x925 equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the sulfur-containing basic compound being used in a total amount of 5xc3x9710xe2x88x925 to 1xc3x9710xe2x88x923 equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, and the sulfur-containing compound being used in an amount of 0.1 to 100 atoms in terms of sulfur atoms based on 1 atom of the alkali metal of the alkali metal compound, so as to form the above aromatic polycarbonate of the present invention.
Thirdly, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as xe2x80x9csecond production method of the present inventionxe2x80x9d hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and a C-radical scavenger, the alkali metal compound being used in an amount of 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x925 equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the phosphorus-containing basic compound being used in a total amount of 5xc3x9710xe2x88x925 to 1xc3x9710xe2x88x923 equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, and the C-radical scavenger being used in an amount of 0.0001 to 5 parts by weight based on 100 parts by weight of the formed aromatic polycarbonate, so as to form the aromatic polycarbonate of the present invention.
In the fourth place, according to the present invention, the above objects and advantages of the present invention are attained by a method for preparing an aromatic polycarbonate (may be referred to as xe2x80x9cthird production method of the present inventionxe2x80x9d hereinafter), which comprises polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A in the form of an orthorhombic crystal and a carbonic acid diester in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound, the alkali metal compound being used in an amount of 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x925 equivalent in terms of alkali metal atoms and the nitrogen-containing basic compound and/or the phosphorus-containing basic compound being used in a total amount of 5xc3x9710xe2x88x925 to 1xc3x9710xe2x88x923 equivalent in terms of nitrogen atoms and/or phosphorus atoms based on 1 mol of the aromatic dihydroxy compound, so as to form the above aromatic polycarbonate of the present invention.
Finally, according to the present invention, the above objects and advantages of the present invention are attained by a molded product of the above aromatic polycarbonate of the present invention.
A preferred embodiment of the present invention will be described in detail hereinafter. A description is first given of the polycarbonate of the present invention.
The main recurring structure of the polycarbonate of the present invention is represented by the following formula (1). 
The polycarbonate of the present invention is characterized in that the total of integrated intensities of all signals detected at four ranges, (A) xcex4=2.14 to 2.17 ppm, (B) xcex4=3.46 to 3.49. ppm, (C) xcex4=3.62 to 3.69 ppm and (D) xcex4=5.42 to 5.46 ppm in the 1H-NMR spectrum measured using heavy chloroform as a solvent is 0.01 to 2.0% of the integrated intensity of a signal (reference signal) derived from a methyl group contained in the recurring unit structure of the polymer detected at a range of xcex4=1.50 to 2.00 ppm in the spectrum.
It is not always known what chemical structures the signals detected at the ranges (A) to (D) are derived from. The above polycarbonate having a specific integrated intensity of a specific signal in the 1H-NMR spectrum is characterized in that it has improved stability against thermal decomposition at a temperature range for melt molding and a molded product obtained by melt molding the polycarbonate has high mechanical strength.
Further, the total of integrated intensities of all signals detected at the above ranges (A) to (D) is preferably 0.01 to 1%, particularly preferably 0.01 to 0.8% of the integrated intensity of the reference signal.
When the total of integrated intensities of all signals detected at the above ranges (A) to (D) is smaller than 0.01% or larger than 2% of the integrated intensity of the reference signal, the above effect of improving heat resistant stability cannot be fully obtained.
In the present invention, the signals of the 1H-NMR spectrum do not have to be detected at all the four NMR spectral ranges, (A) xcex4=2.14 to 2.17 ppm, (B) xcex4=3.46 to 3.49 ppm, (C) xcex4=3.62 to 3.69 ppm and(D) xcex4=5.42 to 5.46 ppm, and may be detected at least one of the four ranges (A) to (D).
The specific component which is the feature of the polycarbonate of the present invention can be detected and quantitatively determined by its NMR spectrum which has been measured for integration of 10,000 times. It is a conventionally known fact that the larger the number of times of integration the greater the signal/noise ratio (S/N ratio) of the spectrum becomes, thereby making it possible to detect and quantitatively determine a trace component contained in a sample more definitely and more accurately. For example, it is known that the S/N ratio when the number of times of integration is 5,000 is about 10 times that when the number of times of integration is 50.
In the present invention, a trace component which cannot be distinguished from noise has newly been discovered in the conventionally obtained NMR spectrum by setting the number of times of integration to 10,000 and increasing the S/N ratio fully. It has further been found that there is the above relationship between the content of the component and the effect of improving the heat resistant stability of a polycarbonate by determining the amount of the component in the order of 10xe2x88x922% of the signal intensity of a methyl group as a comparison standard though the chemical structure which the component is derived from is unknown.
Preferably, in the 1H-NMR spectrum in heavy chloroform of the aromatic polycarbonate of the present invention, the integrated intensity of a signal detected at xcex4=2.14 to 2.17 ppm is 0 to 1.5%, the integrated intensity of a signal detected at xcex4=3.46 to 3.49 ppm is 0 to 0.9%, the integrated intensity of a signal detected at xcex4=3.62 to 3.69 ppm is 0 to 2.0% and the integrated intensity of a signal detected at xcex4=5.42 to 5.46 ppm is 0 to 0.7%, in respect of the integrated intensity of a signal derived from a methyl group detected at xcex4=1.50 to 2.00 ppm.
More preferably, in the 1H-NMR spectrum in heavy chloroform of the aromatic polycarbonate of the present invention, the total of integrated intensities of all signals detected at two ranges, xcex4=3.46 to 3.49 ppm and xcex4=3.62 to 3.69 ppm, is 0.1 to 1.0% in respect of the integrated intensity of a signal derived from a methyl group detected at ∂=1.50 to 2.00 ppm.
The aromatic polycarbonate of the present invention has a viscosity average molecular weight of 10,000 to 100,000, preferably 20,000 to 30,000, more preferably 12,000 to 17,000.
The polycarbonate of the present invention which has a preferred viscosity average molecular weight of 20,000 to 30,000 preferably shows signal intensities in the following 1H-NMR spectrum.
In the 1H-NMR spectrum in heavy chloroform, the integrated intensity of a signal detected at xcex4=2.14 to 2.17 ppm is 0 to 1.0%, the integrated intensity of a signal detected at xcex43.46 to 3.49 ppm is 0 to 0.6%, the integrated intensity of a signal detected at xcex4=3.62 to 3.69 ppm is 0 to 1.0% and the integrated intensity of a signal detected at xcex4=5.42 to 5.46 ppm is 0 to 0.5%, in respect of the integrated intensity of a signal derived from a methyl group detected at xcex4=1.50 to 2.00 ppm.
Further, the polycarbonate having a more preferred viscosity average molecular weight of 12,000 to 17,000 of the present invention preferably shows signal intensities in the following 1H-NMR spectrum.
In the 1H-NMR spectrum in heavy chloroform, the integrated intensity of a signal detected at xcex4=2.14 to 2.17 ppm is 0 to 0.4%, the integrated intensity of a signal detected at xcex4=3.46 to 3.49 ppm is 0 to 0.3%, the integrated intensity of a signal detected at xcex4=3.62 to 3.69 ppm is 0 to 0.2% and the integrated intensity of a signal detected at xcex4=5.42 to 5.46 ppm is 0 to 0.1%, in respect of the integrated intensity of a signal derived from a methyl group detected at xcex4=1.50 to 2.00 ppm.
The aromatic polycarbonate of the present invention is comprising mainly a recurring unit represented by the above formula (1). The recurring unit represented by the above formula (1) accounts for preferably at least 80 mol %, more preferably at least 90 mol %, particularly preferably at least 95 mol % of the total of all the recurring units.
A description is subsequently given of the first production method of the present invention.
The first production method of the present invention comprises the step of polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of an ester exchange catalyst consisting of an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and a co-catalyst consisting of a sulfur-containing compound.
The above method is carried out by a melting process or sold-phase process, preferably by a melting process.
The production of a polycarbonate by the melting process is carried out by stirring an aromatic dihydroxy compound and a carbonic acid diester under normal pressure and/or vacuum nitrogen atmosphere by heating and distilling off the formed alcohol or phenol.
The polycarbonate of the present invention by the melting process can be produced by using diphenyl carbonate as a carbonic acid diester component or a mixture of diphenyl carbonate and di(2-alkoxycarbonylphenyl)carbonate and melt mixing it with 2,2-bis(4-hydroxyphenyl)propane (to be referred to as xe2x80x9cbisphenol Axe2x80x9d hereinafter) and polymerizing them.
For example, the polycarbonate of the present invention can be produced by reacting a dihydroxy compound with a carbonic acid dieter compound at a temperature of preferably 160 to 300xc2x0 C., more preferably 180 to 280xc2x0 C. for preferably 0.2 to 3 hours, more preferably 0.5 to 2 hours, much more preferably 0.6 to 1.5 hours under reduced pressure in the first stage of a reaction, further carrying out the reaction between the dihydroxy compound and the carbonic acid diester compound by increasing the reaction temperature and the vacuum degree of the reaction system, and finally carrying out a polymerization reaction at a reactor inside pressure of 10xe2x88x925 to 0.001 mmHg and a temperature of 290 to 330xc2x0 C. for 10 to 60 minutes.
As described above, the reaction temperature in the latter stage of the reaction for the production of a polycarbonate by the melting process is preferably 290 to 330xc2x0 C., slightly higher than the temperature generally used, which is effective to advantageously obtain a polycarbonate having a specific integrated intensity of a specific signal in the 1H-NMR spectrum of the present invention.
In the latter stage of the reaction, the system is depressurized to make it easy to distill off the formed alcohol or phenol. The inside pressure of the reactor is preferably 0.001 mmHg or less, a higher degree of vacuum than usual, which is effective to advantageously obtain a polycarbonate having a specific integrated intensity of a specific signal in the 1H-NMR spectrum of the present invention.
The polycarbonate having a specific integrated intensity of a specific signal in the 1H-NMR spectrum of the present invention can be thus preferably produced by carrying out a polymerization reaction at a temperature range of 290 to 330xc2x0 C. higher than the regular temperature and at a reactor inside pressure of 0.001 mmHg or less higher than the regular degree of vacuum for 10 to 60 minutes.
Examples of the carbonic acid diester used in the present invention include diphenyl carbonate, ditolyl carbonate, bis(2-chlorophenyl)carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(4-phenylphenyl)carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate and the like.
Out of these, diphenyl carbonate is preferred from the viewpoints of reactivity, stability against the color of the obtained resin and cost.
When diphenyl carbonate and a compound obtained by substituting diphenyl carbonate with alkoxy carbonyl such as di(2-alkoxycarbonylphenyl)carbonate are used in combination as carbonic acid diester components, the polycarbonate having a specific integrated intensity of a specific signal in the 1H-NMR spectrum of the present invention can be advantageously obtained though the details of a chemical reaction are unknown.
Preferred examples of the di(2-alkoxycarbonylphenyl)carbonate include di(2-methoxycarbonyl-phenyl)carbonate, di(2-ethoxycarbonyl-phenyl)carbonate and the like.
It is disclosed by JP-A 61-87724 and JP-A 61-87725 that a terminal hydroxy group exerts a bad influence upon the heat resistant stability of a polycarbonate. Various methods for reducing the number of polycarbonate terminal OH groups are proposed ardently for a melt polymerization method or solid-phase polymerization method in which a large number of terminal hydroxyl groups are essentially existent in the molecule owing to the characteristics of a polymer production process. However, it is also well known that there are limits to the reduction of the number of OH terminal groups.
In contrast to this, since the polycarbonate of the present invention comprises a structural component having a specific chemical shift and integrated intensity for the signal of the 1H-NMR spectrum, it has excellent heat resistant stability without drastically reducing the amount of terminal OH groups.
Further, in a preferred embodiment for attaining the object of the present invention, the amount of the terminal hydroxyl group of the polycarbonate of the present invention is at least 100 chemical equivalents or less, preferably 80 chemical equivalents or less, more preferably 3 to 60 chemical equivalents, particularly preferably 5 to 50 chemical equivalents based on 1 ton of the polymer. Fewer OH terminals groups are more preferred. However, it is extremely difficult to reduce the amount of the OH terminal group to 5 chemical equivalents or less based on 1 ton of the polymer according to the industrial technical standard in the polycarbonate having a target molecular weight.
The amount of the OH terminal group can be inevitably reduced to the above range by a terminal capping agent used as a molecular weight modifier in a phosgene method. In a melt polymerization method or solid-phase polymerization in which a large number of OH terminal groups are formed owing to the characteristics of a reaction process, a special OH terminal group reduction means must be taken to reduce the amount of the OH terminal group to the above range.
For example, the molar ratio of polymerization raw materials charged is controlled. More specifically, the molar ratio of a carbonic acid diester/an aromatic dihydroxy compound when they are charged into a polymerization reactor is set to 1.03 to 1.10, taking the characteristics of the polymerization reactor into account, to carry out polymerization. Alternatively, OH terminal groups are capped by a salicylic acid ester at completion of the polymerization reaction in accordance with a method disclosed by U.S. Pat. No. 5,696,222.
The amount of the salicylic acid ester used is preferably 0.8 to 10 mols, more preferably 0.8 to 5 mols, particularly preferably 0.9 to 2 mols based on 1 chemical equivalent of the terminal OH group before a capping reaction. By adding the salicylic acid ester in that amount, 80% or more of the terminal OH groups can be advantageously capped. Catalysts disclosed by the above patent are preferably used to carry out the capping reaction.
Illustrative examples of the salicylic acid ester include 2-methoxycarbonylphenyl-phenyl carbonate, 2-methoxycarbonylphenyl-2xe2x80x2-methylphenyl carbonate, 2-methoxycarbonylphenyl-4xe2x80x2-ethylphenyl carbonate, 2-methoxycarbonylphenyl-3xe2x80x2-butylphenyl carbonate, 2-methoxycarbonylphenyl-4xe2x80x2-dodecylphenyl carbonate, 2-methoxycarbonylphenyl-4xe2x80x2-hexadecylphenyl carbonate, 2-methoxycarbonylphenyl-2xe2x80x2,4xe2x80x2-dibutylphenyl carbonate, 2-methoxycarbonylphenyl-dinonylphenyl carbonate, 2-methoxycarbonylphenyl-cyclohexylphenyl carbonate, 2-methoxycarbonylphenyl-biphenyl carbonate, 2-methoxycarbonylphenyl-cumylphenyl carbonate and the like.
A polymerization catalyst and a co-catalyst are used to accelerate the rate of polymerization in the first production method of the present invention. A catalyst used as the polymerization catalyst consists of (i) an alkali metal compound and (ii) a nitrogen-containing basic compound and/or a phosphorus-containing basic compound, from the viewpoint of having heat stability or large polymerization rate.
The alkali metal compound used as a catalyst in the present invention is a hydroxide, hydrogencarbonate, carbonate, acetate, nitrate, nitrite, sulfite, cyanate, thiocyanate, stearate, borohydride, benzoate, hydrogenphosphate, bisphenol salt or phenol salt of an alkali metal.
Illustrative examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate, lithium hydrogencarbonate, sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium acetate, potassium acetate, lithium acetate, sodium nitrate, potassium nitrate, rubidium nitrate, lithium nitrate, sodium nitrite, potassium nitrite, rubidium nitrite, lithium nitrite, sodium sulfite, potassium sulfite, lithium sulfite, sodium cyanate, potassium cyanate, lithium cyanate, sodium thiocyanate, potassium thiocyanate, lithium thiocyanate, cesium thiocyanate, sodium stearate, potassium stearate, lithium stearate, cesium stearate, sodium borohydride, potassium borohydride, lithium borohydride, sodium tetraphenylborate, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogenphosphate, dipotassium hydrogenphosphate, dilithium hydrogenphosphate, disodium salts, dipotassium salts, dilithium salts, monosodium salts, monopotassium salts, sodium potassium salts and sodium lithium salts of bisphenol A, sodium salts, potassium salts and lithium salts of phenol, and the like.
A nitrogen-containing basic compound and/or a phosphorus-containing basic compound are/is further used as a catalyst.
Illustrative examples of the nitrogen-containing basic compound include ammonium hydroxides having an alkyl, aryl or alkylaryl group such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide and hexadecyltrimethylammonium hydroxide, basic ammonium salts having an alkyl, aryl or alkylaryl group such as tetramethylammonium acetate, tetraethylammonium phenoxide, tetrabutylammonium carbonates, benzyltrimethylammonium benzoates and hexadecyltrimethylammonium ethoxide, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine and hexadecyldimethylamine, and basic salts such as tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetraphenyl borate and tetramethylammonium tetraphenyl borate.
Illustrative examples of the phosphorus-containing basic compound include phosphonium hydroxides having an alkyl, aryl or alkylaryl group such as tetramethylphosphonium hydroxide, tetraethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, benzyltrimethylphosphonium hydroxide and hexadecyltrimethylphosphonium hydroxide; and basic salts such as tetramethylphosphonium borohydride, tetrabutylphosphonium borohydride, tetrabutylphosphonium tetraphenyl borate and tetramethylphosphonium tetraphenyl borate.
As to the amount of the polymerization catalyst used in the present invention, the alkali metal compound is 1xc3x9710xe2x88x927 to 1xc3x9710xe2x88x925 chemical equivalent based on 1 mol of the aromatic dihydroxy compound and the amount of the nitrogen-containing basic compound and/or the phosphorus-containing basic compound is 5xc3x9710xe2x88x925 to 1xc3x9710xe2x88x923 chemical equivalent based on 1 mol of the aromatic dihydroxy compound to limit the content of a specific component to a specific range.
The equivalent of the alkali metal compound as used herein means the product of the total number of valences of alkali metal elements contained in 1 molecule of the catalyst and the number of mols of the catalyst. When one alkali metal element (monovalent) is contained in 1 molecule of the catalyst, 1 mol of the catalyst is equal to 1 equivalent to the catalyst and when 2 alkali metal elements (monovalent) are contained in 1 molecule of the catalyst, 1 mol of the catalyst is equal to 2 equivalents of the catalyst.
When the amount of the catalyst is below the above range, the catalyst may exert a bad influence upon the physical properties of the obtained polycarbonate or an ester exchange reaction does not proceed fully, whereby a polycarbonate having a desired molecular weight cannot be obtained disadvantageously. When the amount of the catalyst is above the range, the content of a specific component exceeds a specific range disadvantageously.
A sulfur-containing compound is used as a co-catalyst in the present invention. Any sulfur-containing compound may be used without restriction if it contains a sulfur atom in the molecule. Sulfur-containing organic compounds are preferred. Out of these, thiols, thiocyanates, isothiocyanates, thioesters, thioethers, thiocarbonates, thioureas and disulfides are particularly preferred.
The sulfur-containing compound may be an aromatic compound or aliphatic compound. It is preferably an aliphatic compound because it easily obtain effects as the object of the present invention. Out of aliphatic sulfur-containing compounds, what have a boiling point or thermal decomposition point at normal pressure of 100 to 300xc2x0 C. are more preferred.
Thiols include aliphatic thiols such as methanethiol, ethanethiol, propanethiol, butanethiol, 1,2-butanedithiol, 1,4-butanedithiol, octanethiol, decanethiol, octanedithiol, dodecanethiol, 1,10-dodecanedithiol, stearyl mercaptan, docosanethiol, cyclopentyl mercaptan, cyclohexanethiol, 1,4-cyclohexanedithiol, 1,3,5-cyclohexanetrithiol and 4-pentene-1-thiol; and aromatic thiols such as benzenethiol, naphthalenethiol, biphenylthiol and 1,4-phenylenedithiol. Thiols containing different functional groups such as an ester group, ether group, carboxyl group and amino group may be used as desired. The thiols include metal salts of 2-mercaptopropionic acid, 3-mercaptopropionic acid ethyl ester, butylthioglycolate, 16-mercaptododecanoic acid, bis(2-mercaptoethyl)ether, L-cysteine, L-cysteineethyl ester and L-cysteinebutyl ester, 2-mercaptoimidazole and the like.
Thiocyanates include aliphatic thiocyanates such as methane thiocyanate, ethane thiocyanate, ethylene dithiocyanate, propane thiocyanate, butane thiocyanate, butane dithiocyanate, 1,4-butane dithiocyanate, octanethiocyanate, docosanethiocyanate, octanedithiocyanate, 1,10-decanedithiocyanate, docosanedithiocyanate, hexacosanethiocyanate, cyclohexanethiocyanate and 1,4-cyclohexanedithiocyanate; and aromatic thiocyanates such as benzene thiocyanate, naphthalene thiocyanate, 1,4-phenylene dithiocyanate and benzyl thiocyanate. Thiocyanates containing different functional groups such as an ester group and ether group may be used as desired. The thiocyanates include 2-ethoxyethane thiocyanate, 4-methoxycarbonylbenzene thiocyanate and the like.
Isothiocyanates include aliphatic isothiocyanates such as methane isothiocyanate, ethane isothiocyanate, ethane diisothiocyanate, propane isothiocyanate, butane isothiocyanate, butane diisothiocyanate, 1,4-butane diisothiocyanate, octaneisothiocyanate, docosaneisothiocyanate, octanediisothiocyanate, docosanediisothiocyanate, cyclohexane isothiocyanate and 1,4-cyclohexane diisothiocyanate; and aromatic isothiocyanates such as benzene isothiocyanate, naphthalene isothiocyanate and 1,4-phenylene diisothiocyanate. Isothiocyanates having different functional groups such as an ester group and ether group may be used as desired. The isothiocyanates include 2-ethoxybutane isothiocyanate, 4-phenoxyphenyl isothiocyanate and the like.
Thioesters include aliphatic thioesters such as propionic acid ethylthioester and xcex3-thiobutyrolactone; and aromatic thioesters such as benzoic acid methyl thioester. Thioesters containing different functional groups such as an ether group may be used as desired. The thioesters include 2-methoxypropionic acid ethyl thioester, t-butyl-S-(4,6-dimethylpyrimidine-2-yl) and the like.
Thioethers include aliphatic thioethers such as dimethyl sulfide, diethyl sulfide, dibutyl sulfide, di-n-hexyl sulfide, butyloctyl sulfide, trimethylene sulfide, pentamethylene sulfide, 1,3,5-trithiane, 1,3-dithiolan, 1,4,7-trithiacyclodecane and 1,4,7-trithiacyclononane; and aromatic thioethers such as 1,3-bis(phenylthio)propane, diphenyl sulfide, dibenzyl sulfide, dinaphthyl sulfide and bis(2,4-di-n-propylphenyl)sulfide. Thioethers containing different functional groups such as an ester group, ether group, carboxyl group and amino group may be used as desired. The thioethers include 4-ethoxy-n-butyl-hexylthioether, methylmethyl thioacetate, thiomorpholine, 1,4-thioxane, bis(4-methoxycarbonylphenyl)sulfide, 3-butylthiopropionic acid, 2-ethylthiobenzoic acid, 4-butylthiohexylamine, 3-methylthiophenylamine, bis(4-ethoxybenzyl)sulfide and the like.
Thiocarbonates include aliphatic thiocarbonates such as diethyl thiocarbonate, dibutyl thiocarbonate and dimethyl trithiocarbonate; and aromatic thiocarbonates such as diphenyl thiocarbonate. Thiocarbonate containing different functional groups such as an ester group and ether group may be used as desired. The thiocarbonates include bis(2-ethoxyethyl)thiocarbonate, bis(2-acetylethyl)thiocarbonate and the like.
Thioureas include aliphatic thioureas such as thiourea, 1-methyl-2-thiourea, 1,3-diethyl-2-thiourea, 1,3-dibutyl-2-thiourea, 1,3-diisopropyl-2-thiourea and dicyclohexylthiourea; and aromatic thioureas such as 1,3-diphenyl-2-thiourea. Thioureas containing different functional groups such as an ester group, ether group and amino group may be used as desired. The thioureas include 4-methoxycarbonylphenyl-3-phenyl-2-thiourea, 4-phenoxyphenyl-3-phenylthiourea, 2-thiohydantoin, 1,1-thiocarbonylimidazole, 1-cyclohexyl-3-(2-morpholinoethyl)-2-thiourea and the like.
Disulfides include aliphatic disulfides such as dimethyl disulfide, diethyl disulfide, dibutyl disulfide, di-n-hexyl disulfide and butyloctyl disulfide; and aromatic disulfides such as diphenyl disulfide, dibenzyl disulfide, dinaphthyl disulfide and bis(2,4-di-n-propylphenyl)disulfide. Disulfides having different functional groups such as an ester group, ether group, carboxyl group and amino group may be used as desired. The disulfides include 4-ethoxybutylhexyl disulfide, bis(4-methoxycarbonylphenylmethyl)disulfide, S-methylthiocysteine, cystine and the like.
Out of these sulfur compounds, octanethiol, trithiane and thiourea are preferred. These compounds may be used alone or in combination.
The above sulfur compound is used in an amount of 0. 1 to 100 sulfur atoms based on 1 atom of an alkali metal of an alkali metal compound as a catalyst.
The sulfur compound is more preferably used in an amount of 0.3 to 80 sulfur atoms, much more preferably 1 to 50 sulfur atoms based on the same standard.
The time of adding the sulfur-containing compound is not particularly limited but preferably from before an ester exchange reaction to the initial stage of the ester exchange reaction. It is more preferred to add the sulfur-containing compound together with an alkali metal compound as a catalyst. An apparatus used for addition and a material therefor are not particularly limited.
In the present invention, to obtain a polycarbonate suited for the production of thin melt moldings, what has a melt viscosity stability after polymerization of 0.5% or less is preferably used. To set the melt viscositystability of the polycarbonate to 0.5% or less, a specific amount of a melt viscosity stabilizer is added to a polycarbonate after a polycondensation reaction, preferably after the end of a terminal capping reaction. A polycarbonate having low melt viscosity stability is hardly put to practical use because it has low stability at the time of molding and low stability of mechanical properties, especially a drastic reduction in impact resistance, when its moldings are used at high humidity or for a long time.
The melt viscosity stability is evaluated by an absolute value of change in melt viscosity measured under a nitrogen atmosphere at a shearing speed of 1 rad/sec and 30xc2x0 C. for 30 minutes and expressed by change rate per minute.
The melt viscosity stabilizer used in the present invention serves to deactivate part or all of the activity of a polymerization catalyst used at the time of producing a polycarbonate.
As for the addition of the melt viscosity stabilizer, for example, it may be added while a polycarbonate as a reaction product is molten or after a polycarbonate is pelletized and re-molten. In the former, it may be added while the polycarbonate as a reaction product in a reactor or extruder is molten, or a deactivator may be added and kneaded while the polycarbonate obtained after polymerization is pelletized from a reactor through an extruder.
Any known melt viscosity stabilizer may be used, as exemplified by tetrabutylphosphonium octylsulfonate, tetrabutylphosphonium decylsulfonate, tetramethylphosphonium benzene sulfonate, tetrabutylphosphonium benzene sulfonate, tetrabutylphosphonium dodecylbenzene sulfonate, tetrahexylphosphonium dodecylbenzene sulfonate, tetraoctylphosphonium dodecylbenzene sulfonate, tetramethylammonium decylsulfonate, tetraethylammonium benzene sulfonate, tetrabutylammonium dodecylbenzene sulfonate, methylbenzene sulfonate, ethylbenzene sulfonate, butylbenzene sulfonate, octylbenzene sulfonate, phenylbenzene sulfonate, methyl p-toluene sulfonate, ethyl p-toluene sulfonate, butyl p-toluene sulfonate, octyl p-toluene sulfonate, phenyl p-toluene sulfonate, methyl dodecylsulfonate, ethyl hexadecyl sulfonate, propylnonyl sulfonate, butyl decylsulfonate and the like.
Out of these, sulfonic acid compounds such as organic sulfonic acid salts, organic sulfonic acid esters, organic sulfonic anhydrides and organic sulfonic acid betaines are preferred and phosphonium salts of sulfonic acid and/or ammonium salts of sulfonic acid are more preferred because they have the large effect of improving the physical properties such as color, heat resistance and boiling water resistance of a polycarbonate. Out of these, tetrabutylphosphonium dodecylbenzene sulfonate and tetrabutylammonium p-toluene sulfonate are particularly preferred.
The polycarbonate having excellent heat resistant stability of the present invention can be obtained by the abovemethod. A conventionally known processing stabilizer, heat resistant stabilizer, antioxidant, ultraviolet light absorber, antistatic agent, flame retardant, release agent, colorant and the like may be added according to application purpose to form various moldings from the polycarbonate. In this case, if the above additives have a signal at the same ranges as the above four chemical shift ranges in the above 1H-NMR spectrum for specifying the polycarbonate of the present invention, the heat resistant stability improving effect of the additives is irrelevant to the heat resistant stability improving effect of the polycarbonate of the present invention.
A heat stabilizer may be mixed to prevent a reduction in the molecular weight of the polycarbonate of the present invention and deterioration in the color of the polycarbonate of the present invention. Examples of the heat stabilizer include phosphorous acid, phosphoric acid, phosphinous acid, phosphonic acid and esters thereof. For example, trisnonylphenyl phosphite, tris(2,4,-di-tert-butylphenyl)phosphite, 4,4xe2x80x2-biphenylene diphosphonic acid tetrakis(2,4-di-tert-butylphenyl), 4,4xe2x80x2-trimethylphosphate and dimethyl benzene phosphonate are preferably used. These heat stabilizers may be used alone or in combination of two or more. The amount of the heat stabilizer is preferably 0.0001 to 1 part by weight, more preferably 0.0005 to 0.5 part by weight, much more preferably 0.001 to 0.1 part by weight based on 100 parts by weight of the polycarbonate of the present invention.
To further improve releasability from a metal mold at the time of melt molding, a release agent may be mixed with the polycarbonate of the present invention in limits that do not impair the object of the present invention. Examples of the release agent include olefin-based wax, olefin-based wax containing a carboxyl group and/or carboxylic anhydride group, silicone oil, organopolysiloxane, higher fatty acid esters of monohydric and polyhydric alcohols, paraffin wax, beeswax and the like. The amount of the release agent is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the polycarbonate of the present invention.
Out of the higher fatty acid esters, a partial ester or whole ester of a monohydric or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms is preferred. Preferred examples of the partial ester or whole ester of a monohydric or polyhydric alcohol and a saturated fatty acid include glycerin monostearate, triglyceride glycerin stearate and pentaerythritol tetrastearate. The amount of the release agent is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the polycarbonate of the present invention.
The above additives specified by the present invention and the polycarbonate of the present invention can be produced by mixing the above additive compositions by a desired means such as a tumbler, blender, cone screw-type mixer, Banbury mixer, kneading roll, extruder or the like.
A description is subsequently given of the second production method of the present invention. It should be understood that the above description of the first production method of the present invention can be applied to what is not described of the second production method herein directly or with modifications obvious to one of ordinary skill in the art.
The second production method of the present invention is carried out by polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A and a carbonic acid diester in the presence of as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound and a C-radical scavenger.
Preferred examples of the C-radical scavenger include silanes represented by the following formula (A):
R1R2R3SiHxe2x80x83xe2x80x83(A)
wherein R1, R2 and R3 are each independently a hydrogen atom, alkyl group having 1 to 30 carbon atoms, alkoxyl group having 1 to 20 carbon atoms or aryl group having 6 to 20 carbon atoms which may be substituted,
or silanes represented by the following formula (A)-1:
xe2x80x94Oxe2x80x94SiY1Y2Y3xe2x80x83xe2x80x83(A)-1
wherein Y1, Y2 and Y3 are each independently a hydrogen atom, alkyl group having 1 to 20 carbon atoms, alkoxyl group having 1 to 10 carbon groups or aryl group having 6 to 20 carbon atoms which may be substituted,
an acrylate represented by the following formula (B): 
wherein R4 and R5 are each independently a hydrogen atom or alkyl group having 1 to 6 carbon atoms, R6 is a hydrogen atom or methyl group, R7 is a hydrogen atom, alkyl group having 1 to 6 carbon atoms or aryl group having 6 to 10 carbon atoms, R8 and R9 are each independently an alkyl group having 1 to 10 carbon atoms, and m and n are 0, 1 or 2,
and a lactone-based stabilizer represented by the following formula (C): 
wherein R10 is an alkyl group having 1 to 10 carbon atoms, n is an integer of 0 to 3, and Ar is an aromatic group having 6 to 20 carbon atoms which may be substituted.
The definition, function and the like of the C-radical scavenger are described in xe2x80x9cStabilization of Polymeric Materialsxe2x80x9d written by Hans Zweifel, items 2, 1, 2, 5, page 52.
The amount of the C-radical scavenger is preferably 0.0001 to 5 parts by weight, more preferably 0.0005 to 3 parts by weight, much more preferably 0.001 to 1 part by weight, particularly preferably 0.001 to 0.5 part by weight based on 100 parts by weight of the polycarbonate.
When the amount of the C-radical scavenger is smaller than 0.0001 part by weight, its effect of reducing the formation of gel foreign matter and its effect of improving moist heat resistance and color stability are hardly obtained and when the amount is larger than 5 parts by weight, it often exerts a bad influence upon the color, transparency and mechanical properties of the obtained polycarbonate.
In the present invention, when the C-radical scavenger is used to maintain its relationship with the amount of terminal OH groups which is represented by the following formula (I), its effect is large advantageously.
log[OH]+10xe2x89xa6log(a)xe2x89xa6log[OH]+3xe2x80x83xe2x80x83(I)
wherein [OH] is the amount of the terminal OH group of the polycarbonate (eq/ton) and (a) is the amount of the C-radical scavenger added (ppm).
Examples of the silanes represented by the above formula (A) include phenyldimethoxysilane, phenyldimethylsilane, benzyldimethylsilane, 1,2-bis(dimethylsilyl)benzene, 1,4-bis(dimethylsilyl)benzene, bis[(p-dimethylsilyl)phenyl]ether, bis(trimethylsiloxy)ethylsilane, bis(trimethylsiloxy)methylsilane, t-butyldimethylsilane, di-t-butylmethylsilane, di-t-butylsilane, dimethylethoxysilane, diphenylmethylsilane, diphenylsilane, ethylbis(trimethylsiloxy)silane, ethyldimethylsilane, hexylsilane, methyldiethoxysilane, methyltris(dimethylsiloxy)silane, n-octadecylsilane, n-octylsilane, pentamethylcyclopentasiloxane, phenyldiethoxysilane, phenyldimethylsilane, phenylmethylsilane, phenylsilane, tetraethylcyclotetrasiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, 1,1,4,4-tetramethyldisilylethylene, tri-t-butylsilane, triethoxysilane, triethylsilane, tri-n-hexylsilane, triisobutylsilane, triisopropoxysilane, triisopropylsilane, triphenylsilane and the like.
Examples of the acrylate represented by the above formula (B) include 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-t-pentyl-6-(3-t-pentyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-t-butylphenyl)ethyl]-4,6-di-t-butylphenyl acrylate, 2-[1-(2-hydroxy-3-t-butyl-5-methylphenyl)ethyl]-4-methyl-6-t-butylphenyl acrylate, 2-[1-(2-hydroxy-3-t-pentyl-5-methylphenyl)ethyl]-4-methyl-6-t-pentylphenyl acrylate, 2,4-di-t-pentyl-6-(3,5-di-t-pentyl-2-hydroxy-benzyl)phenyl acrylate, 2,4-di-t-butyl-6-(3,5-di-t-butyl-2-hydroxy-benzyl)-phenyl acrylate and the like.
It is understood that the second production method of the present invention is a method in which the above C-radical scavenger is used in place of the sulfur-containing compound used in the first production method.
A description is subsequently given of the third production method of the present invention. It should be understood that the above description of the first production method of the present invention can be applied to what is not described of the third production method herein directly or with modifications obvious to one of ordinary skill in the art.
The third production method of the present invention is carried out by polycondensing an aromatic dihydroxy compound comprising mainly bisphenol A in the form of an orthorhombic crystal and a carbonic acid diester using in the presence of, as an ester exchange catalyst, an alkali metal compound and a nitrogen-containing basic compound and/or a phosphorus-containing basic compound.
In the third production method, the orthorhombic bisphenol A is used as bisphenol A.
A monoclinic system is known as the crystal structure of bisphenol A, that is, 2,2-bis(4-hydroxyphenyl)propane, in addition to an orthorhombic system. The inventors of the present invention have found that when 2,2-bis(4-hydroxyphenyl)propane having an orthorhombic crystal structure is used, the obtained polycarbonate has excellent color.
The definite reason why the color of the obtained polymer becomes excellent when orthorhombic 2,2-bis(4-hydroxyphenyl)propane is used is unknown. The present inventors presume that there is a difference in surface activity for adsorbing crystal impurities between the orthorhombic system and the monoclinic system.
Methods of obtaining orthorhombic 2,2-bis(4-hydroxyphenyl)propane include one in which 2,2-bis(4-hydroxyphenyl)propane is purified by fractional melting crystallization and one in which a crystal adduct of 2,2-bis(4-hydroxyphenyl)propane is obtained, decomposed and purified.
In the third production method of the present invention, a co-catalyst consisting of a sulfur-containing compound used in the first production method of the present invention or a C-radical scavenger used in the second production method of the present invention does not always need to be used.
The thus produced aromatic polycarbonate of the present invention specified by the specific signal in the above 1H-NMR spectrum can be formed into various moldings such as films and sheets. It can be particularly advantageously used as a substrate for optical recording media such as optical disks including CDs and DVD-RAMs.